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Full text of "Diseases Of The Nose Throat And Ear"

CHAPTER 73
CONGENITAL DEAFNESS

A normal child learns to speak because it hears its mother and those around
it speaking. The desire to imitate is inborn, and the child gradually learns to
reproduce the sounds that it hears. If a child cannot hear the speech of others
it will not learn to speak itself. Even a child with normal hearing, if brought
up in total isolation by deaf-mute parents, both of whom suffer from acquired
deaf-mutism, would not learn to speak—indeed such a case has occurred. It
should be noted that in about 99 per cent of cases of mutism or dumbness the
trouble is due to deafness. There are rare instances in which the patient suffers
from congenital aphasia, and such a child, even when blindfolded, will carry
out whispered orders, e.g. 'raise your arms' and 'shut the door'. The causes
of congenital deafness may be classified as prenatal, perinatal and postnatal.

I. PRENATAL CAUSES

A. Familial defects of the labyrinth are responsible for the condition known
as sporadic congenital deafness. Complete absence of the labyrinth has been
described. Both the bony and membranous cochlea may be malformed. As
a rule, however, only the membranous cochlea and saccule are involved, the
utricle and semicircular canals being normal (Figs. 213-216). In the great
majority of cases both ears are affected. The anatomical findings may be
divided into two types—primary changes in the cochlear duct and saccule,
and primary degenerate atrophy of the spiral ganglion.

The incidence of hereditary deafness is determined by Mendelian law and
the occurrence of deafness in certain families is well known. If hearing
people carrying deafness marry pure hearing people, no deafness results.
But if by chance—and the chance is bound to come—two hybrids (hearing
people carrying deafness) marry, then deaf children must follow.

Among the recognized syndromes in which deafness may be noted are:

i. Waardenburg's syndrome which consists of some or all of the following-
perceptive deafness of any severity either unilaterally or bilaterally; shorten-
ing of the eye fissures; hypertrichosis of the eyebrows which may meet in the
midline; differently coloured eyes (heterochromia iridium); and a white
forelock.

ii. Klippel-FeiVs syndrome in which the neck is short or absent with a low
hairline at the back and limited head movements. There is paralysis of the
external rectus of one or both eyes and a perceptive deafness which is often
severe.

iii. Treacher Collins* syndrome in which there are deformed malar bones
and infra-orbital ridges so that the palpebral fissures slope downwards; the
lower eyelids are notched and deficient in lashes medially; there may be

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